An MRI review of acquired corpus callosum lesions

Incidence of Hearing Loss in Corpus Callosum Agenesis

OBJECTIVES

Congenital corpus callosum agenesis (CCA) is one of the congenital anomalies in newborns, which usually presents with syndromic features. It can be asymptomatic or have variable neurological deficits. Some studies demonstrated that hearing loss can occur in patients with CCA; however, the exact prevalence remains unclear. Therefore, we aimed to investigate the prevalence of hearing loss in CCA using data from newborn hearing screening in a single tertiary referral center.

METHODS

A total of 126 patients with CCA combined with hearing loss diagnosed at our hospital from November 2005 to November 2022 were retrospectively included in our study. All patients had at least one screening or diagnostic auditory brainstem response result. Brain ultrasonography and magnetic resonance imaging were used to diagnose CCA.

RESULTS

Among 126 patients, 93 had automated auditory brainstem response within a month from birth. Of the 93 patients, 20 (21.5%) had a "refer" result in the screening tests in at least one ear. The final incidence of hearing loss in patients with CCA was 16.1%. We observed no hearing loss in 22 patients with isolated CCA.

CONCLUSIONS

Patients with CCA have a higher incidence of hearing loss. However, this is likely related to the concurrent condition of patients. CCA seems not to be a risk factor for hearing loss.

Clinico-radiologic subtypes and therapeutic observation of acute Marchiafava-Bignami disease

We aimed to investigate the clinico-radiologic features of acute Marchiafava-Bignami disease (MBD) and its evolutionary process after effective treatment through subgroup comparison. The clinical and MRI data of 23 patients with acute MBD were retrospectively analyzed and divided into type A (12 cases, with entire callosal involvement) and type B (11 cases, with focal callosal involvement). The clinical assessments and MRI findings (before and after treatment) were compared between the two subtypes. Compared with type B, type A had lower MoCA (Montreal Cognitive Assessment) scores at admission (16.50 ± 1.73 vs 18.27 ± 1.68, P = 0.021) and were more common with extracallosal involvement (66.67% vs 18.18%, P = 0.036) and longer illness duration (18.3 ± 2.1 days vs 15.6 ± 2.4 days, P = 0.012). During the treatment, the residual lesion in the splenium was more common in type A (58.33% vs 9.09%, P = 0.027). After treatment, the MoCa scores of both subtypes gradually increased (P < 0.001), and the callosal and extracallasal lesions disappeared completely. Clinico-radiologic typing of acute MBD is related to the severity of early symptoms, but not to the prognosis. Complete clinico-radiologic recovery is possible for both subtypes with combined treatment. The clinico-radiologic reversibility is helpful for accurate diagnosis and therapeutic evaluation.

Diffusion-Restricted Lesions of the Splenium: Clinical Presentation, Radiographic Patterns, and Patient Outcomes

Background and Objectives

Diffusion-restricted (DR) lesions of the splenium are encountered in a wide variety of pathologies, and their significance is often unclear. We sought to report the spectrum of clinical presentations, neuroimaging patterns, and the predictors of radiographic and clinical outcomes from DR splenial lesions.

Methods

This was a single-center, retrospective cohort study from January 1, 2009, to August 1, 2020. A consecutive sample of 3,490 individuals who underwent brain MRI with reported corpus callosum lesions during the study period were evaluated for DR lesions in the corpus callosum. DR lesions were defined as increased signal intensity on diffusion-weighted imaging sequences with decreased signal intensity on apparent diffusion coefficient. Patients with prior neurosurgical procedures, hemorrhage-associated DR, anoxic brain injury, and chronic or previously known or characterized disease processes in the corpus callosum were excluded. Clinical and radiologic outcomes were ascertained, including readmissions within 1 year, in-hospital mortality rates, and resolution of DR at first follow-up imaging. Outcomes were defined a priori.

Results

Two hundred patients met criteria for inclusion. The average age was 57 years (standard deviation 19 years). Near half of the patients were women (47%). Encephalopathy (55%), focal weakness (46.5%), and cortical signs (44%) were the most common presenting clinical features. Thirty-five cases (17.5%) had features consistent with cytotoxic lesions of the corpus callosum (CLOCCs). Vascular causes were most frequent (61%), followed by malignancy-related (15%) and trauma (8%). In-hospital mortality occurred in 8.5% of cases, 46.5% were readmitted to the hospital within 1 year, and 49.1% of patients had resolution of the splenial DR at the next scan. Backward stepwise regression models showed that mass effect was negatively associated with splenial DR resolution (odds ratio [OR]: 0.12, confidence interval [CI] 0.03-0.46, p = 0.002). Encephalopathy was significantly associated with in-hospital mortality (OR: 4.50, CI 1.48-17.95, p = 0.007). Patients with a CLOCC had less frequent readmissions at 1-year compared with patients without a CLOCC, p = 0.015.

Discussion

Vascular DR lesions of the splenium were more common than CLOCCs and other etiologies in this cohort. While splenial DR lesions can present a clinical challenge, their associated clinical and radiographic characteristics may predict outcome and guide prognosis.

An elderly man with mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) without neuropsychiatric sequelae

Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is less common in the elderly, and most have some sequelae. However, even in the elderly, MERS may have a good prognosis, and a specific treatment is not always required.

Corpus callosum lesions are associated with worse cognitive performance in cerebral amyloid angiopathy

The impact of vascular lesions on cognition is location dependent. Here, we assessed the contribution of small vessel disease lesions in the corpus callosum to vascular cognitive impairment in cerebral amyloid angiopathy, as a model for cerebral small vessel disease. Sixty-five patients with probable cerebral amyloid angiopathy underwent 3T magnetic resonance imaging, including a diffusion tensor imaging scan, and neuropsychological testing. Microstructural white-matter integrity was quantified by fractional anisotropy and mean diffusivity. Z-scores on individual neuropsychological tests were averaged into five cognitive domains: information processing speed, executive functioning, memory, language and visuospatial ability. Corpus callosum lesions were defined as haemorrhagic (microbleeds or larger bleeds) or ischaemic (microinfarcts, larger infarcts and diffuse fluid-attenuated inversion recovery hyperintensities). Associations between corpus callosum lesion presence, microstructural white-matter integrity and cognitive performance were examined with multiple regression models. The prevalence of corpus callosum lesions was confirmed in an independent cohort of memory clinic patients with and without cerebral amyloid angiopathy (n = 82). In parallel, we assessed corpus callosum lesions on ex vivo magnetic resonance imaging in cerebral amyloid angiopathy patients (n = 19) and controls (n = 5) and determined associated tissue abnormalities with histopathology. A total number of 21 corpus callosum lesions was found in 19/65 (29%) cerebral amyloid angiopathy patients. Corpus callosum lesion presence was associated with reduced microstructural white-matter integrity within the corpus callosum and in the whole-brain white matter. Patients with corpus callosum lesions performed significantly worse on all cognitive domains except language, compared with those without corpus callosum lesions after correcting for age, sex, education and time between magnetic resonance imaging and neuropsychological assessment. This association was independent of the presence of intracerebral haemorrhage, whole-brain fractional anisotropy and mean diffusivity, and white-matter hyperintensity volume and brain volume for the domains of information processing speed and executive functioning. In the memory clinic patient cohort, corpus callosum lesions were present in 14/54 (26%) patients with probable and 2/8 (25%) patients with possible cerebral amyloid angiopathy, and in 3/20 (15%) patients without cerebral amyloid angiopathy. In the ex vivo cohort, corpus callosum lesions were present in 10/19 (53%) patients and 2/5 (40%) controls. On histopathology, ischaemic corpus callosum lesions were associated with tissue loss and demyelination, which extended beyond the lesion core. Together, these data suggest that corpus callosum lesions are a frequent finding in cerebral amyloid angiopathy, and that they independently contribute to cognitive impairment through strategic microstructural disruption of white-matter tracts.

Global Rostral Midbrain Syndrome (GRMS) and Corpus callosum infarction in the context of shunt overdrainage

We report 3 cases of Global rostral midbrain syndrome (GRMS) and Corpus Callosum (CC) infarction, in the context of hydrocephalus followed by shunt dysfunction and slit ventricles. Prior shunt implantation had been indicated for adult-onset hydrocephalus secondary to aqueductal stenosis of varying causes. All three patients had been stable for months before developing repeated shunt dysfunctions, ultimately progressing to parkinsonism, Parinaud syndrome, akinetic mutism, pyramidal signs, cognitive impairment, CC infarction and slit ventricles, in the context of CSF overdrainage. Parkinsonism-related symptoms responded to dopa in all cases, but Parinaud syndrome and cognitive impairment persisted. Although GRMS has been described in the context of a transtentorial pressure gradient after shunt blockage, in these three cases with similar clinical presentation, reverse transtentorial pressure gradient and slit ventricles due to shunt overdrainage was the likely cause. The authors discuss the role of CC infarction and provide a detailed analysis after gathering previously described data, to unify information under a recognizable clinical entity and better understand the underlying pathophysiology, treatment options and outcome.

Associations of histological and molecular alterations with invasion of the corpus callosum in gliomas

BACKGROUND

Glioma invading the corpus callosum (CC) accounts for approximately 14% of gliomas and is thought to be more aggressive. However, there is still a lack of studies on the pathogenesis and molecular features of this condition. Here, we examined the occurrence association of CC invasion with respect to patients' clinical, pathological, and genetic characteristics.

METHODS

First, a cohort of 331 patients was included, with 86 cases (26%) that were diagnosed with invasion glioma. They were all analyzed for basic clinical and pathological characteristics and four routinely tested glioma molecular markers. Second, 29 pairs of patients who underwent deep sequencing of 68 glioma molecular alterations were selected from both groups for in-depth analysis.

RESULTS

The results of the first part showed that there was no difference between the two groups in terms of the basic factors in univariate analysis, while in multivariate logistic analysis, WHO grade was the risk factor for CC invasion (p = 0.001). The results of the second part showed that the paired groups had different genetic expression profiles, which highlighted glioma invading the CC as a distinct biological entity. PDGFRA mutation (PDGFRAmut) was present in 9 patients with invasive gliomas (31%), but only in one case (3.4%) in the control group (OR 17.331; 95% CI 1.987-151.156).

CONCLUSION

Our data revealed the clinical, pathological, and genetic characteristics of glioma invading the CC and showed that it may be associated with glioma WHO grade and PDGFRAmut, but not other factors. Thus, the risk signaling pathway may offer potential therapeutic targets for this disease.

Reversible Splenial Lesion Syndrome Associated with Encephalitis/Encephalopathy and Hyponatremia

Reversible splenial lesion syndrome (RESLES) is a rare occurrence with a broad clinical and radiological spectrum due to several conditions and diseases. Generally, clinical symptoms of RESLES include mildly altered states of consciousness, delirium, and seizures. RESLES can be shown in conjunction with central nervous system infections, especially in children. Hyponatremia is also described as a potential cause of reversible splenial lesions. Reversible signal changes on diffusion-weighted images are detected in patients for diagnosis. The prognosis is usually good but it depends on the underlying disease, neurological and imaging findings. Here we present two pediatric patients with RESLES accompanied by hyponatremia.

Treatment-related transient splenial lesion of the Corpus Callosum in patients with neuropsychiatric disorders: a literature overview with a case report

Introduction: Transient-localized lesions of the splenium of the corpus callosum (SCC) have been described in various clinical conditions, some of them being attributed to the withdrawal of psychotropic drugs. The pathophysiology of the lesion reflects cytotoxic edema and reversible demyelination.Areas covered: The present article aimed at reviewing cases of transient SCC lesion exclusively related to changes in pharmacotherapy. It also reports the original case of a patient receiving a complex psychopharmacological therapy who developed a transient SCC lesion investigated by magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and pharmacogenetic profiling.Expert opinion: To date, only one review on the subject has been published, analyzing 22 cases of transient SCC lesion arising in epileptic patients on antiepileptic therapy. It hypothesized that the nature of the lesion is a cytotoxic edema and the cases described in the subsequent 14 years seem to support this hypothesis. The authors reported the case of an Italian-Egyptian patient who developed a transient SCC lesion after the rapid withdrawal of Carbamazepine and Lurasidone. The lesion completely disappeared from the MRI performed after 1 month. Patient's ethnic group and its pharmacogenetic profile were considered as possible causes of altered drug metabolism and, likely, of the SCC lesion.

Uncovering convolutional neural network decisions for diagnosing multiple sclerosis on conventional MRI using layer-wise relevance propagation

Machine learning-based imaging diagnostics has recently reached or even surpassed the level of clinical experts in several clinical domains. However, classification decisions of a trained machine learning system are typically non-transparent, a major hindrance for clinical integration, error tracking or knowledge discovery. In this study, we present a transparent deep learning framework relying on 3D convolutional neural networks (CNNs) and layer-wise relevance propagation (LRP) for diagnosing multiple sclerosis (MS), the most widespread autoimmune neuroinflammatory disease. MS is commonly diagnosed utilizing a combination of clinical presentation and conventional magnetic resonance imaging (MRI), specifically the occurrence and presentation of white matter lesions in T2-weighted images. We hypothesized that using LRP in a naive predictive model would enable us to uncover relevant image features that a trained CNN uses for decision-making. Since imaging markers in MS are well-established this would enable us to validate the respective CNN model. First, we pre-trained a CNN on MRI data from the Alzheimer's Disease Neuroimaging Initiative (n = 921), afterwards specializing the CNN to discriminate between MS patients (n = 76) and healthy controls (n = 71). Using LRP, we then produced a heatmap for each subject in the holdout set depicting the voxel-wise relevance for a particular classification decision. The resulting CNN model resulted in a balanced accuracy of 87.04% and an area under the curve of 96.08% in a receiver operating characteristic curve. The subsequent LRP visualization revealed that the CNN model focuses indeed on individual lesions, but also incorporates additional information such as lesion location, non-lesional white matter or gray matter areas such as the thalamus, which are established conventional and advanced MRI markers in MS. We conclude that LRP and the proposed framework have the capability to make diagnostic decisions of CNN models transparent, which could serve to justify classification decisions for clinical review, verify diagnosis-relevant features and potentially gather new disease knowledge.

Defining the Normal Dorsal Contour of the Corpus Callosum with Time

BACKGROUND AND PURPOSE

Morphological changes of the corpus callosum have been associated with a large number of congenital neurocognitive and psychiatric disorders. Focal defects or notches of the dorsal surface of the corpus callosum have not been well characterized. Our purpose was the following; 1) to characterize the dorsal contour of the corpus callosum during the life span, 2) to characterize the relationship of contour deviations to neighboring vessels, and 3) to determine whether contour deviations are congenital or acquired.

MATERIALS AND METHODS

We retrospectively reviewed normal sagittal T1-weighted brain MR images. A "notch" was defined as a concavity in the dorsal surface at least 1 mm in depth. The corpus callosum was considered to be "undulating" if there were >2 notches, including an anterior and posterior notch. The presence of a pericallosal artery and its relationship to a notch were assessed.

RESULTS

We reviewed 1639 MR imaging studies, spanning 0-89 years of age. A total of 1102 notches were identified in 823 studies; 344 (31%) were anterior, 660 (60%) were posterior, and 98 (9%), undulating. There was a positive correlation between the prevalence (P < .001) and depth (P = .028) of an anterior notch and age and a negative correlation between the prevalence of a posterior notch and age (P < .001). There was no difference between patient sex and corpus callosum notching (P = .884). Of the 823 studies with notches, 490 (60%) were associated with a pericallosal artery (P < .001).

CONCLUSIONS

The prevalence and depth of notches in the anterior corpus callosum increase significantly with age; this finding suggests that most notches are acquired. There is a significant positive association between the presence of a corpus callosum notch and adjacent pericallosal arteries, suggesting that this may play a role in notch formation.

Neuromyelitis Optica Spectrum Disorders: Spectrum of MR Imaging Findings and Their Differential Diagnosis

Neuromyelitis optica (NMO) is an autoimmune demyelinating disorder for which the aquaporin-4 (AQP4) water channels are the major target antigens. Advances in the understanding of NMO have clarified several points of its pathogenesis, clinical manifestations, and imaging patterns. A major advance was the discovery of the AQP4 antibody, which is highly specific for this disorder. Descriptions of new clinical and radiologic features in seropositive patients have expanded the spectrum of NMO, and the term NMO spectrum disorder (NMOSD) has been adopted. NMOSD is now included in a widening list of differential diagnoses. Acknowledgment of NMOSD imaging patterns and their mimicry of disorders has been crucial in supporting early NMOSD diagnosis, especially for unusual clinical manifestations of this demyelinating disease. This pictorial review summarizes the wide imaging spectrum of NMOSD and its differential diagnosis, as well as its historical evolution, pathophysiology, and clinical manifestations. ^©RSNA, 2018.

Surgical Resection of Anterior and Posterior Butterfly Glioblastoma

BACKGROUND

Evidence suggests a survival benefit for patients with glioblastoma who undergo maximal safe surgical resection. Not all glioblastomas are amenable to surgical resection and anatomic location is one potentially limiting factor. Glioblastomas that invade the corpus callosum and cross midline to the contralateral hemisphere-butterfly glioblastomas (bGBMs)-are one subgroup of tumors traditionally deemed inoperable.

METHODS

We evaluate the management of bGBMs at our institution to assess whether surgical resection is feasible, safe, and more effective than biopsy. We retrospectively reviewed our institutional brain tumor registry for all adult patients treated for glioblastoma (World Health Organization grade IV) between 2004 and 2016 to identify all bGBMs.

RESULTS

Survival between biopsy and resection was assessed using the Kaplan-Meier model. Twenty-nine (3.8%) of 764 newly diagnosed GBMs were identified as bGBM. Of these, 9 patients (31.0%) underwent surgical resection and 20 patients (69.0%) underwent biopsy. Five patients (55.6%) in the surgical resection group had 98% extent of resection or greater. Median survival of our entire cohort of patients was 3.3 months. Median survival was higher in the surgical resection groups (7.8 vs. 2.8 months; P = 0.0019). Increased age is independently associated with increased risk of death, and adjuvant therapy is independently associated with prolonged survival.

CONCLUSIONS

Surgical resection of butterfly glioblastoma prolongs survival without increased risk of permanent neurologic deficit. Both anterior and posterior bGBMs can be resected safely.

Unusual presentation of a severely ill patient having severe fever with thrombocytopenia syndrome: a case report

BACKGROUND

Severe fever with thrombocytopenia syndrome is an emerging infectious disease caused by a novel phlebovirus belonging to the family Bunyaviridate. Emergence of encephalitis/encephalopathy during severe fever with thrombocytopenia syndrome progression has been identified as a major risk factor associated with a poor prognosis. Here we report the case of a severely ill patient with severe fever with thrombocytopenia syndrome virus-associated encephalitis/encephalopathy characterized by a lesion of the splenium, which resolved later.

CASE PRESENTATION

A 56-year-old Japanese man presented with fever and diarrhea, followed by dysarthria. Diffusion-weighted magnetic resonance imaging demonstrated high signal intensity in the splenium of the corpus callosum. The severe fever with thrombocytopenia syndrome virus genome was detected in our patient's serum, and the clinical course was characterized by convulsion, stupor, and hemorrhagic manifestations, with disseminated intravascular coagulation and hemophagocytic lymphohistiocytosis. Supportive therapy not including administration of corticosteroids led to gradual improvement of the clinical and laboratory findings, and magnetic resonance imaging demonstrated resolution of the splenial lesion. The serum severe fever with thrombocytopenia syndrome viral copy number, which was determined with the quantitative reverse-transcription polymerase chain reaction, rapidly decreased despite the severe clinical course. Our patient's overall condition improved, allowing him to be eventually discharged.

CONCLUSIONS

Patients with encephalitis/encephalopathy due to severe fever with thrombocytopenia syndrome virus infection may have a favorable outcome, even if they exhibit splenial lesions and a severe clinical course; monitoring the serum viral load may be of value for prediction of outcome and potentially enables the avoidance of corticosteroids to intentionally cause opportunistic infection.

[Standartization of MRI studies in multiple sclerosis]

The use of magnetic resonance imaging (MRI) in patients with multiple sclerosis has markedly increased in recent years. The main task of the MRI studies after the diagnosis of multiple sclerosis is to assess the dynamics of MRI for determining disease progression and monitoring the efficacy of therapy. In this regard, it is very important to obtain the most identical baseline and follow-up MRI that is possible when a single standard protocol is used. This article presents the protocol of brain MRI and spinal cord MRI and interpretation of MRI studies in patients with multiple sclerosis.

Diffusion MRI features of acute encephalopathy due to stopping steroid medication abruptly in congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is characterized by adrenal steroid biosynthesis defect. Steroid replacement therapy should be performed regularly in these patients. Adrenal crisis may be present in acute stress due to increased cortisol requirements or in steroid deficiency due to stopping steroid medication abruptly. In patients with acute adrenal insufficiency, severe hypotension or hypovolemic shock occurs typically. Acute encephalopathy can be seen due to hypoxia, hypervolemia, or hypoglycemia. Diffusion restriction can be seen in cortical-subcortical regions of frontal and parieto-occipital lobes and in splenium of corpus callosum. In CAH patients with neurologic symptoms, Diffusion weighted images (DWI) is very important in the diagnosis and follow-up of acute encephalopathy.

Evidence-based guidelines: MAGNIMS consensus guidelines on the use of MRI in multiple sclerosis-clinical implementation in the diagnostic process

The clinical use of MRI in patients with multiple sclerosis (MS) has advanced markedly over the past few years. Technical improvements and continuously emerging data from clinical trials and observational studies have contributed to the enhanced performance of this tool for achieving a prompt diagnosis in patients with MS. The aim of this article is to provide guidelines for the implementation of MRI of the brain and spinal cord in the diagnosis of patients who are suspected of having MS. These guidelines are based on an extensive review of the recent literature, as well as on the personal experience of the members of the MAGNIMS (Magnetic Resonance Imaging in MS) network. We address the indications, timing, coverage, reporting and interpretation of MRI studies in patients with suspected MS. Our recommendations are intended to help radiologists and neurologists standardize and optimize the use of MRI in clinical practice for the diagnosis of MS.

Corpus callosum involvement and postoperative outcomes of patients with gliomas

Corpus callosum involvement is associated with poorer survival in high grade glioma (HGG), but the prognostic value in low grade glioma (LGG) is unclear. To determine the prognostic impact of corpus callosum involvement on progression free survival (PFS) and overall survival (OS) in HGG and LGG, the records of 233 glioma patients treated from 2008 to 2011 were retrospectively reviewed. Preoperative magnetic resonance (MR) images were used to identify corpus callosum involvement. Age, sex, preoperative Karnofsky performance scale, postoperative Eastern Cooperative Oncology Group (ECOG) score and extent of resection (EOR) were evaluated with respect to PFS and OS. The incidence of corpus callosum involvement was similar among HGG (14 %) and LGG (14.5 %). Univariate analysis revealed that PFS and OS were significantly shorter in both WHO grade II and grade IV glioma with corpus callosum involvement (both, p < 0.05). Multivariate analysis showed that grade II glioma with corpus callosum involvement have shorter PFS (p = 0.03), while EOR, instead of corpus callosum involvement (p = 0.16), was an independent factor associated with PFS in grade IV glioma (p < 0.05). Corpus callosum involvement was no longer significantly associated with OS after adjusting age, gender, EOR, preoperative and postoperative performance status (p = 0.16, 0.17 and 0.56 in grade II, III and IV gliomas, respectively). Corpus callosum involvement happened in both LGG and HGG, and is associated with lower EOR and higher postoperative ECOG score both in LGG and HGG. Corpus callosum involvement tends to be an independent prognostic factor for PFS in LGG, but not for OS in LGG or in HGG.

Overcoming the effects of false positives and threshold bias in graph theoretical analyses of neuroimaging data

Graph theory (GT) is a powerful framework for quantifying topological features of neuroimaging-derived functional and structural networks. However, false positive (FP) connections arise frequently and influence the inferred topology of networks. Thresholding is often used to overcome this problem, but an appropriate threshold often relies on a priori assumptions, which will alter inferred network topologies. Four common network metrics (global efficiency, mean clustering coefficient, mean betweenness and smallworldness) were tested using a model tractography dataset. It was found that all four network metrics were significantly affected even by just one FP. Results also show that thresholding effectively dampens the impact of FPs, but at the expense of adding significant bias to network metrics. In a larger number (n=248) of tractography datasets, statistics were computed across random group permutations for a range of thresholds, revealing that statistics for network metrics varied significantly more than for non-network metrics (i.e., number of streamlines and number of edges). Varying degrees of network atrophy were introduced artificially to half the datasets, to test sensitivity to genuine group differences. For some network metrics, this atrophy was detected as significant (p<0.05, determined using permutation testing) only across a limited range of thresholds. We propose a multi-threshold permutation correction (MTPC) method, based on the cluster-enhanced permutation correction approach, to identify sustained significant effects across clusters of thresholds. This approach minimises requirements to determine a single threshold a priori. We demonstrate improved sensitivity of MTPC-corrected metrics to genuine group effects compared to an existing approach and demonstrate the use of MTPC on a previously published network analysis of tractography data derived from a clinical population. In conclusion, we show that there are large biases and instability induced by thresholding, making statistical comparisons of network metrics difficult. However, by testing for effects across multiple thresholds using MTPC, true group differences can be robustly identified.

Clinicoradiological spectrum of reversible splenial lesion syndrome (RESLES) in adults: a retrospective study of a rare entity

The presence of reversible lesions that involve the splenium of the corpus callosum (SCC) has been reported in patients with a broad spectrum of diseases and conditions and is referred to as reversible splenial lesion syndrome (RESLES).To describe the clinicoradiological features and establish a clinical position for this disease, we retrospectively examined the clinicoradiological features of adult RESLES patients, as well as discuss the potential pathophysiological mechanisms of this disease.The clinical and MRI findings of patients who presented with RESLES accompanied by symptoms of neurological disorders were retrospectively reviewed. The patients were classified into 2 subgroups (favorable and poor outcome subgroups), which corresponded to the severity of the disability using the Modified Oxford Handicap Scale. In addition, we compared the clinical and neuroimaging features between the 2 outcome subgroups.Eight patients with RESLES associated with various diseases and conditions were included. The clinical presentation was nonspecific; however, MRI exhibited consistent lesions in the SCC with a hypointensity on apparent diffusion coefficient maps and a hyperintensity via diffusion-weighted imaging, which disappeared after a variable lapse. The number of patients with a severe disturbance of consciousness, extracallosal lesions, or diffuse slow waves in the poor outcome subgroup was significantly increased compared with the favorable outcome subgroup (P < 0.05). Thus, the clinicoradiological spectrum of RESLES could be classified into 2 principal categories according to differential outcomes.RESLES is a rare entity with a broad clinicoradiological spectrum because of the various diseases and conditions. Although the overall symptoms of RESLES patients tend to be alleviated, the prognosis of patients with a severe disturbance of consciousness, extracallosal lesions, or diffuse slow waves is likely unfavorable.